These steps worked for me running on Windows 10, but should work on other windows versions except as noted below. First, download the g90updatefw program, by clicking on the following link:
Then, download the display unit firmware, by clicking on the following link:
Then, download the main unit firmware, by clicking on the following link:
Now, the g90updatefw program and the 2 firmware files are in your Downloads folder.
In this step we will attempt to determine which com port is attached to the G90 serial cable. This may be different on Windows versions 7, 8, or 11 Right click on the Windows Start Button (in the lower left), then click on Device Manager. Then double-click on Ports. While the ports are displayed, if you plug and unplug the G90 USB serial cable, a COM port should appear and disappear. Take note of the com port number. On my system it is COM4.
Open a command prompt in Administrator mode by typing cmd in the windows search bar and selecting "Run as administrator".
Now, you need to change to the Downloads directory (folder). Type this command:
Now, you should be able to run the following command to update the main unit, after plugging in the USB serial cable into the back of the unit. Make sure to use the COM number found previously.
g90updatefw G90_MainUnit_Fw_V1.79b03.xgf COM4
And this command should update the display unit, with the cable in the correct jack on the display unit, with the correct COM port.
g90updatefw G90_DispUnit_Fw_V1.79b03.xgf COM4
Please let me know if you find mistakes in these steps or if you run into problems.